METHOD FOR PRODUCING OPTICAL INFORMATION RECORDING MEDIUM AND OPTICAL INFORMATION RECORDING MEDIUM
In case a convex portion acting as a protector is formed on a signal face of a disc by a liquid material such as radiation cure resin, two substantially concentric concave portions are preliminarily provided on a substrate. A liquid material is dripped onto a region interposed between the concave portions and is cured such that the convex portion having desired height and width can be formed on the region.
The present invention generally relates to an optical information recording medium and its manufacturing method and more particularly, to a method of forming a convex portion on, for example, a disc and a medium formed with the convex portion.
BACKGROUND ARTRecently, researches on various optical information recording techniques are pursued in the field of information recording. Since the optical information recording facilitates higher density and enables recording and reproduction in noncontact state, a wide range of applications for performing the optical information recording at low cost are being made. Optical discs in current use include a compact disc (CD) in which an information layer is provided on a transparent resinous substrate having a thickness of 1.2 mm and is protected by an overcoat layer and a digital versatile disc (DVD) in which two transparent resinous substrates each having a thickness of 0.6 mm are bonded to each other and an information layer is provided on one or both of the substrates.
In recent years, in order to raise recording density of the optical discs, a method in which a numerical aperture (NA) of an objective lens is increased and a method in which a wavelength of a laser in use is reduced are under study. At this time, as a thickness of a recording and reproducing base layer, i.e., one substrate at a side upon which a laser beam is incident becomes smaller, influence exerted on a laser spot by aberration can be lessened further and thus, a permissible value of a tilt angle of the disc can be increased further. Thus, as disclosed in, for example, Japanese Patent Laid-Open Publication No. 8-235638 (1996), a Blu-ray Disc is proposed in which the thickness of the recording and reproducing base layer is set to about 0.1 mm, the NA is set to abut 0.85 and the wavelength of the laser is set to about 400 nm.
At present, the Blu-ray Disc is commercially available and used as a rewritable disc which is contained in a cartridge. However, if a read-only disc or a write once read many disc is put on the market as the Blu-ray Disc in the future, it may be strongly desired that such discs also be used in an uncovered state as in the CD and the DVD. At this time, when a user tries to directly place the disc on a table or pick up the disc from the table, there is a risk that recording and reproduction cannot be performed on the disc due to damage to a recording and reproducing face of the disc. In order to obviate such a risk, it is preferable that a location projecting more than the recording and reproducing face of the disc be provided on the recording and reproducing face. Hereinafter, the projecting location on the recording and reproducing face is referred to as a “protector”.
Generally, in the CD and the DVD, the protector is formed at the time of injection molding of the substrate. However, in the Blu-ray Disc, after the substrate has been injection molded, it is necessary to form a thin light-transmissible layer on the recording and reproducing face or an intermediate layer for a multi-layer construction as disclosed in, for example, Japanese Patent Laid-Open Publication No. 2002-260307 (2002). Thus, if the protector is present on the substrate, these formation steps may become complicated or drop in accuracy. Therefore, the protector should be preferably formed after formation of the light-transmissible layer.
In order to form the protector after formation of the light-transmissible layer, a method may be initially devised in which a protector member is bonded to the substrate by a seal or adhesive. However, this method is likely to entail high cost and its boding strength is apt to be insufficient. Thus, from inexpensive and simple viewpoints, it is considered to adopt a method in which radiation cure resin is dripped onto the disc and then, is cured.
DISCLOSURE OF INVENTION (Problems to be Solved by the Invention)However, prior art has such major problems that due to the liquid material of the protector, its height becomes insufficient when its width is taken into consideration, while its width becomes unnecessarily large when its height is increased sufficiently.
(Means for Solving the Problems)In order to solve the above problems of prior art, a manufacturing method of an optical information recording medium, according to the present invention is characterized in that a liquid material is dripped onto a region bounded by a concave portion on a recording and reproducing face of the optical information recording medium and is cured so as to form a convex portion on the region. By the manufacturing method of the present invention, the convex portion having desired height and width can be easily formed by the liquid material such as radiation cure resin. Since the convex portion acting as a protector can be easily formed afterwards, the protector is not required to be provided on a substrate beforehand, which is advantageous for formation of a light-transmissible layer by spin coating and a two-layer processing.
In the manufacturing method of the present invention, the region is preferably interposed between two substantially concentric concave portions. Thus, the convex portion having the desired height and width can be formed easily.
In the manufacturing method of the present invention, it is preferable that a plurality of the regions each surrounded by the concave portion are provided. Thus, a plurality of the convex portions can be formed easily.
In order to solve the above problems of prior art, a manufacturing method of an optical information recording medium, according to the present invention is characterized in that a liquid material is dripped onto a protrusion on a recording and reproducing face of the optical information recording medium and is cured so as to form a convex portion on the protrusion. By the manufacturing method of the present invention, the convex portion having desired height and width can be easily formed by the liquid material such as radiation cure resin. Since the convex portion acting as a protector can be easily formed afterwards, the protector is not required to be provided on a substrate beforehand, which is advantageous for formation of a light-transmissible layer by spin coating and a two-layer processing.
In the manufacturing method of the present invention, it is preferable that the liquid material is radiation cure resin. Thus, the convex portion can be formed at low cost.
In the manufacturing method of the present invention, the concave portion is preferably formed at the time of injection molding of a substrate. Thus, the concave portion can be formed easily.
In order to solve the above problems of prior art, an optical information recording medium of the present invention includes two or more concave portions which are provided on a recording and reproducing face so as to bound at least one region and a convex portion which is formed on the region. By the optical information recording medium of the present invention, it is possible to obtain the inexpensive optical information recording medium including the convex portion having a stable shape.
Meanwhile, an optical information recording medium of the present invention includes at least one protrusion which is provided on a recording and reproducing face and a convex portion which is formed on the protrusion. By the optical information recording medium of the present invention, it is possible to obtain the inexpensive optical information recording medium including the convex portion having a stable shape.
In the optical information recording medium of the present invention, it is preferable that the convex portion is higher than a surface of a light-transmissible layer. Thus, the convex portion can act as a protector for preventing damage to the surface of the light-transmissible layer.
In the optical information recording medium of the present invention, the convex portion preferably has a width of 1 mm or more. Thus, it is possible to obtain the optical information recording medium including the convex portion having a sufficient strength.
(Effects of the Invention)In the optical information recording medium and its manufacturing method, according to the present invention, in case the light-transmissible layer is manufactured from the liquid material such as the radiation cure resin, the protector having the stable shape can be manufactured, so that the optical information recording medium formed with the protector can be manufactured at low cost.
In accordance with the present invention, the above advantageous effects can be gained.
Hereinafter, embodiments of the present invention are described with reference to the drawings. Unless otherwise specified, the drawings are illustrated by sectional views. In case two portions are symmetrical with respect to an axis in the drawings, only one of the two portions may be shown by omitting the other portion.
First EmbodimentHere, one concrete example of a manufacturing method of the optical information recording medium of the present invention is described. As shown in
As shown in
As shown in
When radiation cure resin 120 is dripped onto the land 115 disposed between the two grooves 106 and 107 of the disc formed with the light-transmissible layer 104 as shown in
In this embodiment, the protector 105 has a height of about 200 μm from a coated surface of the land 115. The protector 105 has a function of spacing a recording and reproducing face of the optical information recording medium away from a table 114 as shown in
As shown in
A case in which the protector 105 is formed by providing the grooves 106 and 107 as in the present invention and a comparative example in which the protector 105 is formed without providing such grooves are shown in
Meanwhile, the manufacturing method of the present invention can be applied to not only a so-called single-layer optical disc having the single signal recording layer as shown in
When the light-transmissible layer 104 is formed by radiation cure resin by clogging the central bore 103 with a cap 110, a case in which the protector 105 is not yet formed as in the present invention and a comparative example in which the protector 105 has already been formed are, respectively, shown in
Furthermore, if the two-layer process of
Therefore, if the protector 105 is formed after formation of the light-transmittable layer 104 as in this embodiment of
Meanwhile, in this specification, the term “radiation” is used to mean any electromagnetic wave capable of curing the radiation cure resin, for example, a concept including infrared ray, visible light ray, ultraviolet ray and X-ray. Hence, the radiation cure resin includes thermosetting resin.
In this embodiment, a read-only optical disc is recited as an example. However, this embodiment may also be applied to a write once read many type or a rewritable type recording and reproducing optical disc.
Second EmbodimentIn a second embodiment of the present invention, one example of a manufacturing method of an optical information recording medium is described with reference to
For example, in
Meanwhile, the protectors 205 may be formed on all the lands 215 but may also be formed on several ones of the lands 215. For example, as shown in
In a third embodiment of the present invention, one example of a manufacturing method of an optical information recording medium is described with reference to
In
In a fourth embodiment of the present invention, one example of a manufacturing method of an optical information recording medium is described with reference to
In
The low protrusion 406 may annularly extend continuously as shown in
The embodiments of the present invention have been described above by reciting the examples. However, the present invention is not limited to the above embodiments but can be applied to various modifications based on a technical idea of the present invention.
INDUSTRIAL APPLICABILITYThe optical information recording medium and its manufacturing method of the present invention are useful for facilitating stable manufacture of the protector from the liquid material such as the radiation cure resin.
Claims
1-23. (canceled)
24. A method of manufacturing an optical information recording medium, said method comprising:
- dripping a liquid material onto a protrusion on a recording and reproducing face of the optical information recording medium; and
- curing the liquid material on the protrusion so as to form a convex portion on the protrusion.
25. The method as claimed in claim 24, wherein said optical information recording medium has a plurality of protrusions and the convex portion is formed so as to straddle the plurality of protrusions.
26. The method as claimed in claim 24, wherein the liquid material is radiation cure resin.
27. The method as claimed in claim 24, wherein the liquid material is thermosetting resin.
28. The method as claimed in claim 24, wherein the convex portion is disposed inside a clamp region of the optical information recording medium.
29. The method as claimed in claim 24, wherein the convex portion is disposed between a clamp region and a signal region of the optical information recording medium.
30. The method as claimed in claim 24, wherein the convex portion is formed after formation of a light transmissible layer.
31. The method as claimed in claim 30, wherein the light-transmissible layer is formed by radiation cure resin.
32. The method as claimed in claim 30, wherein the light-transmissible layer is formed by a sheetlike substrate and adhesive mass.
33. The method as claimed in claim 30, wherein the light-transmissible layer is formed by a sheetlike substrate and radiation cure resin.
34. An optical information recording medium comprising:
- two or more concave portions which are provided on a recording and reproducing face so as to bound at least one region; and
- a convex portion which is formed on the region.
35. An optical information recording medium comprising:
- at least one protrusion which is provided on a recording and reproducing face; and
- a convex portion which is formed on the protrusion.
36. The optical information recording medium as claimed in claim 34, wherein the convex portion is formed by radiation cure resin.
37. The optical information recording medium as claimed in claim 35, wherein the convex portion is formed by radiation cure resin.
38. The optical information recording medium as claimed in claim 34, wherein the convex portion is higher than a surface of a light-transmissible layer.
39. The optical information recording medium as claimed in claim 38, wherein the convex portion is higher than the surface of the light-transmissible layer by 50 μm or more.
40. The optical information recording medium as claimed in claim 34, wherein the convex portion has a width of 1 mm or more.
Type: Application
Filed: Sep 5, 2005
Publication Date: Jan 29, 2009
Inventor: Kazuya Hisada (Osaka)
Application Number: 10/584,948
International Classification: G11B 7/00 (20060101); B05D 5/06 (20060101);